Add volume management to AVR

tests/test_panel.py

@@ -240,6 +240,20 @@ class PanelTest(unittest.TestCase):
         self.assertTrue(all(isinstance(r["volume"], int) for r in state["rooms"]))
         self.assertEqual([r["play_state"] for r in state["rooms"]], ["play", "play"])
 
+    def test_state_carries_the_avrs_own_volume(self):
+        """The AVR's card has a level like every other, and it is the
+        player's own -- not the group's, even while it leads one."""
+        self.heos.volumes[AVR_PID] = 37
+        self.panel.join("lego_room")
+        self.assertEqual(self.panel.state()["avr"]["volume"], 37)
+
+    def test_the_avrs_volume_moves_like_a_rooms(self):
+        self.heos.volumes[AVR_PID] = 23
+        self.assertEqual(self.panel.step_volume("avr", 1), 25)
+        self.assertEqual(self.heos.volumes[AVR_PID], 25)
+        self.assertEqual(self.panel.set_volume("avr", 40), 40)
+        self.assertEqual(self.panel.volume("avr"), 40)
+
     def test_state_reports_trouble_instead_of_blowing_up(self):
         self.panel.heos.host = "127.0.0.1"
         self.panel.heos.port = 1          # nothing is listening there